Application of miniature circuit breaker in small capacity terminal power distribution system

[application] small circuit breaker in small capacity terminal distribution in: (a) there are two main line typical scheme of terminal distribution box the traditional status of the traditional terminal power distribution box, as shown in Figure 1, one is power by (DZ10 or DZ20) air circuit breaker (some also increased fuse after entering the bus) distribution box, each output by the fuse, as shown in Figure 1...

(a) the current situation of the traditional terminal distribution box

There are two main line typical traditional scheme of terminal distribution box, as shown in Figure 1, one is power by (DZ10 or DZ20) air circuit breaker (some added fuse) bus after entering the distribution box, each output by the fuse, such as the program in Figure 1 (a); two is the bus power source through the air circuit breaker in distribution box, each output by the switch (you can also type DZ10 or type DZ20 air circuit breaker and fuse) control, such as the program in Figure 1 (B). Air circuit breaker into the power line as the main power supply on-off operation with short circuit protection and back stage, in order to prevent the occurrence of low current air circuit breaker fails to short-circuit the rapid and reliable action, added the fuse each line, each line as the main switch isolating switch scheme (a) in various the outlet can be both fuse isolating switch function. In Figure 1 the distribution scheme (b) also has the use of DZ type air circuit breaker as the outlet switch. For small capacity terminal distribution, these combinations, the knot line program mainly exists as follows:

1 occupies a larger space. Using fuse as distribution box of short circuit protection, the distribution box is larger, occupies a large space, less beautiful, when the number of output of the power distribution box is particularly prominent.

2 the connection point of the circuit, the installation of the process, the reliability is poor. The use of fuses as short-circuit protection of distribution box, fuse and terminal connection point and contact reliability, maintenance workload, and it is easy to appear the phenomenon of bad contact, resulting in motor open phase operation was burned.

3 operation is not safe, it is not convenient. Only use fuses as branch line protection, distribution box without isolating switch of each branch, each branch alone need to stop operation power transmission method, only through the melting heart removed or installed back to fuse to complete, not only trouble, but also poses a risk of electric shock.

4 high cost. When the DZ type air circuit breaker is used as the outlet switch, the space is large, and the cost is high.

Analysis and verification of the characteristics of (two) miniature circuit breakers

1 Characteristics of miniature circuit breakers

DZ47-63 type miniature circuit breaker as an example, according to the release form is divided into D type and C type two, mainly used in AC 50Hz, rated voltage 380V, for overload and short circuit protection of distribution line rated short-circuit current does not exceed 6000A, can also be used as a frequent on-off operation and conversion in. C type for lighting and civil distribution, D for industrial power distribution. The main technical performance parameters of DZ47-63 (D) type miniature circuit breakers are introduced:

(1) protection function: overload long time delay and short circuit protection function.

(2) the current tripping characteristic: as shown in table 1.

(3) rated breaking capacity: 4000A, 220V, 6000A, 380V.

(4) mechanical electrical life: 4000 times.

Miniature circuit breaker between DZ47-63 type C and type D two release form is that the former requires 5 times the rated current for 0 seconds without tripping, the latter is 7 times the rated current for 0 seconds without tripping, bear the instantaneous peak current capability and reliability of the motor starting current avoid higher.

2 Application in terminal distribution analysis

According to the technical parameters provided by the manufacturer, the C type DZ47-63 type miniature circuit breaker can be used for the distribution and control of lighting circuit, and the D type can be used for low-voltage power distribution and control of industrial power. Load change lighting circuit while the larger, but the impact load is relatively small, therefore, the application of miniature circuit breakers in building lighting circuit has been more popular, but the impact load of great industrial power distribution, small circuit breakers are seldom involved in. The reason is that the small size of the circuit breaker is too small, the reliability of the impact load, short-circuit protection, overload protection performance and mechanical electrical life and so on are questioned.

The performance analysis of the small circuit breaker used in the low-voltage power distribution system is as follows:

(1) the reliability of the control of impact load from table 1 shows that the D type miniature circuit breaker tripping form can not release in 0 seconds at 7 times the rated current.

The small starting current of three-phase AC asynchronous motor rated current is 4 ~ 7 times, the peak value of short duration, can fully meet the requirements of motor start without tripping.

(2) the performance of short circuit protection from table 1 shows that the D type miniature circuit breaker tripping form can release in 0 seconds at 14 times the rated current, rated breaking capacity: 380V 4000A, 220V 6000A. To meet the small capacity power

Short circuit protection requirements for power distribution.

(3) overload protection performance table 1 shows that the D type miniature circuit breaker tripping form in 120 seconds off at 2.55 times the rated current, motor overload protection and can meet the requirements of distribution line.

(4) electricapparatuslife electricapparatuslife DZ47-63 small circuit breaker: 4000, according to the survey, failure of the mechanical and electrical failure in the application of miniature circuit breaker to control the lighting distribution, also should be able to meet the requirements of industrial power distribution.